共查询到20条相似文献,搜索用时 78 毫秒
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为研究热冲压工艺参数加热温度、保温时间及冷却水流速等对热冲压零件微观组织及力学能的影响,对TRIP钢在不同工艺参数条件下进行热冲压成形工艺试验,测量冲压件的力学性能并观察其显微组织。结果表明,TRIP钢板经过热冲压成形并淬火后,形成均匀细小的马氏体组织,抗拉强度大大提高。并确定了热冲压工艺参数的最佳选择范围为加热温度810~860℃、保温时间150~250 s、冷却水速度大于0.7 m/s。 相似文献
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《金属热处理》2017,(12)
为了改善精密滚珠丝杠感应淬火后的表层硬度及硬度均匀性,提高耐磨性及寿命,利用Gleeble-1500D热模拟试验机,以50℃/s的加热速度,将55CrMo钢试样分别加热到800、850、900、950、1000、1100和1200℃,并在相应温度分别保温8、16和32 s,然后以50℃/s的冷却速度进行冷却,研究加热温度及保温时间对55CrMo钢相变温度、微观组织、显微硬度的影响。结果表明:在快速加热条件下,55CrMo钢奥氏体化温度升高;升高加热温度和延长保温时间均有利于促进奥氏体化均匀,抑制贝氏体转变,有利于增加均匀细小的马氏体组织,改善丝杠表面淬硬层硬度值的均匀性;55CrMo钢感应淬火时,应将感应加热的温度控制在900~1000℃范围内。 相似文献
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《热加工工艺》2015,(13)
为了弄清热镦温度对复杂型面钛合金自锁螺母成形性能的影响,对加热温度与加热参数的关系,不同温度下钛合金螺母的成形性能进行了试验研究。结果表明:感应加热功率为20.5~32.6 k W、加热时间在5~9 s内可使钛合金螺母坯料的加热温度控制在800~950℃之间,变形程度为55.3%时复杂型面钛合金螺母毛坯可以实现一次镦锻成形;在实际镦锻过程中,激烈变形产生的变形热导致加热温度为950℃的样品实际温度已超过相转变点,进而引起晶粒急剧粗化;在800~900℃温度区间,随加热温度的增加,钛合金的成形能力提高,在900℃的加热温度下,钛合金自锁螺母呈现较好的成形性能。 相似文献
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利用材料万能试验机、金相显微镜和透射电镜研究了热成形钢WHT1300HF在850、900和950℃分别保温5 min,以及在900℃分别保温2、10和15 min奥氏体化处理并模拟热冲压淬火后的组织和性能变化规律。结果表明,随着奥氏体化温度从850℃升高到950℃,试验钢的屈服强度先下降后有所升高,抗拉强度和伸长率均呈明显的下降趋势,显微硬度则迅速升高;而试验钢的强度、伸长率和显微硬度均随奥氏体化时间的延长呈明显的下降趋势。另外,在850℃和900℃保温2 min奥氏体化处理,试验钢的微观组织中均存在铁素体,而在900℃及以上的温度或在900℃保温5 min及更长时间奥氏体化处理后均为全马氏体组织;奥氏体晶粒大小随加热温度的升高和保温时间的延长逐渐增大,但加热温度对奥氏体晶粒的长大作用更显著。 相似文献
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基于Merklein流变应力模型、Kirkaldy相变动力学模型和Koistinen方程,建立了热-力-相耦合有限元模型,得到了硼钢22Mn B5在热冲压过程中温度、组织和维氏硬度的分布规律。仿真结果表明:当模具感应加热端温度升至400℃时,加热端板料的冷却速度为13.6℃·s~(-1),低于马氏体形成冷却速度27℃·s~(-1)。根据感应加热方式研制出变强度冲压件的热冲压新型分区模具,并进行了热冲压试验。结果表明:该新型模具升温速度快,升温至400℃只需5 s,同一模具可冲压不同加热区形状的零件。冲压件加热区为贝氏体组织,硬度为260 HV;过渡区为马氏体、贝氏体和铁素体多相混合组织,硬度为340 HV;低温区为板条状马氏体组织,硬度为491 HV。研制出的新型热冲压模具可以获得变强度热冲压件,满足汽车B柱类零件变强度的要求。 相似文献
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热成形过程中的加热温度对板料性能影响非常显著。本文研究了在不同加热温度下板料的微观组织,并通过氧化法和晶粒边界腐蚀法显示22MnB5钢奥氏体晶界,测定板料晶粒尺寸的变化。结果表明:随着加热温度的升高,板料微观组织马氏体板条束宽度和奥氏体晶粒尺寸随之增大,在900℃时晶粒尺寸适中且分布较为均匀,且氧化法较晶粒边界腐蚀法显示的晶粒尺寸偏细。测定板料抗拉强度,在900℃时出现峰值,且此温度下板料硬度值约为550HV,因此,加热温度900℃,保温时间3min,板料综合性能较好。 相似文献
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发动机齿环常规生产工艺包括下料→冲孔→扩孔成形→正火→酸洗→校正等过程。使用箱式炉正火,工件氧化严重,变形大,能耗大。采用手工校正薄壁环形件的椭圆度和平面度,劳动强度大,质量难以保证,更不能满足我厂索菲姆发动机批量生产的要求。由于可控硅中频感应加热的... 相似文献
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Free forming of locally heated specimens 总被引:1,自引:0,他引:1
O. Okman M.
zmen H. Huwiler A.E. Tekkaya 《International Journal of Machine Tools and Manufacture》2007,47(7-8):1197-1205
A novel manufacturing method is investigated, in which a steep temperature gradient within the workpiece is induced to facilitate material flow locally. By this method, complex shapes can be formed without complicated dies. The feasibility of the idea is analyzed experimentally and numerically. Local heating is realized either by means of induction or laser heating. Experiments using materials 16MnCr5, X5CrNi18/9, and Ti6Al4V have been conducted under various process conditions. These experiments have also been modeled by finite element method (FEM) validating the analysis procedure. Electromagnetic models are used to analyze the heat generation pattern on the workpiece by induction. It is found that the most important process parameters are the thermal diffusivity and the temperature sensitivity of the flow curve of the workpiece material. The lower the thermal diffusivity and the higher the temperature sensitivity, the more differentiated local shapes can be formed. For the analyzed geometries, induction heating has been observed to be more effective. Deformation rate and initial workpiece geometry have also a significant effect on the achievable local deformations. Various failure modes such as unintended deformations, damage by fracture, and melting of the workpiece material are described. It is concluded that the new idea of forming local shapes by local heating is a feasible and controllable manufacturing alternative. 相似文献
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The load relaxation behavior of small Elgiloy helical extension springs has been evaluated by a combined experimental and
modeling approach. Isothermal, continuous heating, and interrupted heating relaxation tests of a specific spring design were
conducted. Spring constants also were measured and compared with predictions using common spring formulas. For the constant
heating rate relaxation tests, it was found that the springs retained their strength to higher temperatures at higher heating
rates. A model, which describes the relaxation behavior, was developed and calibrated with the isothermal load relaxation
tests. The model incorporates both time-independent deformation mechanisms, such as thermal expansion and shear modulus changes,
as well as time-dependent mechanisms such as primary and steady state creep. The model was shown to accurately predict the
load relaxation behavior for the continuous heating tests, as well as for a complex stepwise heating thermal cycle. The model
can be used to determine the relaxation behavior for any arbitrary thermal cycle. An extension of the model to other spring
designs is discussed. 相似文献
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钢铁零件在空气介质中加热会发生氧化脱碳,不仅造成材料损失,也影响零件的热处理质量。硼砂水溶液、硼酸酒精溶液、氯化物水溶液和QW—F1保护剂均可以有效防止钢铁零件在空气中加热过程中发生氧化脱碳。介绍了这些防护剂的防护原理、主要成分、操作方法和应用实例。 相似文献
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采用有限元数值模拟技术,分析了12V240 机车曲轴坯的感应电加热制度。按照镦锻工艺的要求,提出了改进的加热制度,为实际生产应用提供了依据和参考。 相似文献
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针对现行加热温度制度中加热温度过高而造成能耗较高、生产成本较高的压力,武钢热轧总厂三分厂经过充分研究分析,进行了降温轧制实践,部分商品材和供冷轧用带钢的热轧加热温度从1250℃大幅降低至1170℃,使轧线成材率提高约030%,吨钢加热平均能耗下降约0040GJ/t,产生了良好的经济效益和社会效益。 相似文献
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Summary Hydrogen‐assisted cracking in the fusion zone (FZ) was studied, using flux‐cored wire (AWS E 70T5 and AWS E 120 T5‐K4) and a CO2 + 5% H2 gas mixture to induce high values of diffusible hydrogen in high strength, low alloy steel (HSLA‐80) welds. An acoustic emission measurement system (AEMS) based on a root mean square (RMS) voltmeter was coupled to the implant test apparatus (NF 89–100) to determine energy, amplitude and number of signals. Using optical microscopy and scanning electron microscopy (SEM), it was observed that, in all tests, cracks were initiated in the partially molten zone and propagated in the coarse‐grained region of the heat affected zone (HAZ) when E 70 T5 wire was used and quasi‐cleavage (QC) fracture mode was predominant. When E 120 T5 K.4 wire was used, the cracks were propagated vertically across the FZ and the mixed fracture mode was predominant. A significant relationship between acoustic emission (AE) parameters and fracture modes was found in the cracking mechanism. 相似文献